1) Field of the Invention
The present invention relates to an actuator that uses a blade spring, and an object detecting apparatus with the actuator.
2) Description of the Related Art
Recently, an object detecting apparatus is mounted on mobile bodies such as automobiles or motorcycles. This object detecting apparatus detects presence/absence of an object (for example, a car, a human being, a guard rail etc.) around the mobile body and/or a distance to the object.
The object detecting apparatuses generally employ laser radar and/or a millimeter wave radar to detect objects. The laser radar irradiates laser light from a phototransmitting element, this laser light is reflected from the object, and the presence/absence of the object and the distance up to the object is detected from a time required for receiving of the laser light (reflected light) from the object by a photoreceiving element that is provided in the object detecting apparatus. On the other hand, the millimeter wave radar transmits electric waves (millimeter waves) from an antenna that is provided in the object detecting apparatus, these electric waves are reflected at the object that outside the mobile body, then the reflected electric waves (reflected waves) are received by the antenna or another antenna that is provided for reception, and the presence or the absence of the object and the distance up to the object is detected from a phase difference when the reflected waves are received by the antenna.
In the object detecting apparatus, an actuator that changes a direction of irradiation of the laser light or the electric waves by moving a lens in the laser radar and the antenna in the millimeter wave radar to search over a wide range outside the mobile body is used (for example, refer to Japanese Patent Application Laid Open Publication No. H10-123252). This actuator includes a spring (a coil spring 14 according to Japanese Patent Application Laid-open Publication No. H10-123252) that is provided between a movable member on which the optical element such as the lens is fixed (a lens holder 15 according to Japanese Patent Application Laid-open Publication No. H10-123252), and a fixed member (a base member 13 according to Japanese Patent. Application Laid-open Publication No. H10-123252). Moreover, this movable member can be moved either in upward and downward or to left and right by a driving unit (a coil unit 17 that is fixed to the base member 13 through a permanent magnet 18 that is fixed to the lens holder 15 and a side frame 16 according to Japanese Patent Application Laid-open Publication No. H10-123252). By allowing the laser light that is irradiated from the fixed member or the phototransmitting element that is provided on the mobile body on which this fixed member is mounted (a laser light source 8 according to Japanese Patent Application Laid-open Publication No. H10-123252) to be incident on the lens of the movable member that is moved by the driving unit, the direction of irradiation of the laser light can be changed.
Incidentally, in recent years, with an improvement in safety consciousness and increased needs for prevention of collision and safety during collision etc., it has become necessary to widen a range of detection of the object detecting apparatus, as well as to have detailed information of outside of the mobile body. In other words, it has become necessary to increase an amount of movement of the movable member on which the lens or the antenna is installed and moreover to secure an accuracy of positioning of the movable member that has a large amount of movement. Therefore, to detect a position of the movable member with respect to the fixed member and an amount of displacement of the movable member, detecting the position of the movable member and the amount of displacement of the movable member by using a photosensor or a magnetic sensor can be taken into consideration. However, in a general low cost photosensor or magnetic sensor, a range of detection of an optical strength or magnetic strength being narrow, everything such as a position of a movable member with a large amount of movement and an amount of displacement of the movable member cannot be detected. Therefore, conventionally, a general low cost sensor with a narrow range of detection could not be used and it has been necessary to use a sensor with a wide range of detection as a position detector, thereby causing a problem of raising the cost of the object detecting apparatus comparatively.